Republican presidential candidate, former Pennsylvania Sen. Rick Santorum speaks in front of the Supreme Court in Washington, Monday, as the court began three days of arguments on the health-care law signed by President Obama.

Santorum took his campaign to the steps of the Supreme Court Monday, and has been using every opportunity he can to hammer home his main point: That Mitt Romney's health-care law in Massachusetts was the "blueprint" upon which Obamacare is based, and that as a result, Romney can't credibly criticize what is, for many Republicans, the most hated achievement of the Obama administration.

Romney has said he will fight to repeal Obama's law, and has argued that the Massachusetts law was different in many respects – particularly since it was what the voters there wanted.

Criticizing "Romneycare" has been a favorite tactic of Santorum's (and other GOP candidates) for months; the Supreme Court case just helps by moving it front and center in the news.

"Why would the Republican Party nominate someone who agrees with that [individual] mandate, on the most important issue of the election? That's why it's become so important because it's the establishment types who don't mind Obamacare," Santorum said on CNN Sunday.

It's certainly unlikely that the issue is going to do much to boost Santorum, who is badly trailing Romney in the delegate account and faces far less friendlier states in April primaries. The only question at this point for Santorum seems to be how much longer he'll stay in the race.

But how much does this it hurt Romney?

Obama's staff have been underlining Romney's Massachusetts health plan too, with David Plouffe, a senior adviser, calling him the "godfather" of the administration's health-care plan.

But not everyone agrees that Romney's health-care history will hurt him.

"To the extent that attacks on President Barack Obama’s health-care reform are good politics, the candidate best able to make them is Mitt Romney," argue Paul Goldman and Mark Rozell in a Politico column. (Mr. Goldman is a former chairman of Virginia’s Democratic Party, and Mark Rozell is a professor of public policy at George Mason University.)

They point out that aspects of ObamaCare are popular, and say that Romney has an edge in criticizing it since he can't be portrayed as totally lacking in compassion the way some other Republicans might be – analagous to Nixon going to China.

Romney "would be the first GOP nominee in nearly 50 years with a proven track record on health care who has been praised by Democrats –including the president – as fair and compassionate. He can’t be demonized as an out-of-touch, uncompassionate, hard-right ideologue on this issue," they write.

That may be a hard distinction for Romney to make to die-hard conservatives in November – but many of those voters may still see him as a better alternative than Obama.

Meanwhile, as much as Santorum and other conservatives are emphasizing the Supreme Court case now, it's hard to know how much of an issue it will be this fall. If the Supreme Court does in fact rule that part or all of the health-care law is unconstitutional, then it's hardly likely to stay at the top of voters' minds.

For now, though, expect Santorum – but not Romney – to get as much news mileage as he can out of the hearings this week.